function adjust(){
  let deviceWidth=document.documentElement.clientWidth || window.innerWidth
  if(deviceWidth >750){
    deviceWidth=750
  }
  if(deviceWidth < 320){
    deviceWidth=320
  }
  document.documentElement.style.fontSize=(deviceWidth/7.5)+'px'
  document.body.style.fontSize=0.30+'rem'
  document.body.style.padding=0
  document.body.style.margin=0
}

adjust()

window.onresize=function (){
  adjust()
}